Windows 7 Tip: 
Gmail Manager is a Firefox extension that allows you to manage multiple gmail accounts and receive new mail notifications.
Gmail Manager will display account details that include unread messages, spam messages, saved drafts, labels with new mail, space used and new mail snippets.
Features
* Manage multiple Gmail accounts
* Receive new mail notifications
* Support for Gmail hosted accounts
* Tooltip with account details and new mail snippets
* One-click access for loading your Gmail account
i prefer the yahoo mail … it has a better filter spam